Known surround sound audio systems for vehicles utilize a single mapping of the surround sound audio signals to the vehicle speakers, regardless of the fader position. The fader and amplifier are used to vary only the power/gain of the surround sound signals to bias the sound toward the front or rear of the vehicle as controlled by a user of the system. The mapping of each surround sound signal to a particular speaker is constant for all positions of the fader.
FIG. 1 illustrates a vehicle V and a typical ten speaker audio/video surround sound system S for same. The audio/video system includes a head unit HU as is known in the art, that typically includes and/or is connected to various audio/video output devices such as an AM/FM tuner, a CD player, mp3 player, a DVD video player, and one or more video display monitors M for displaying video images to occupants of the vehicle. As shown in FIG. 2, the system S includes a DVD video player or other multi-channel source 10 connected to a surround sound decoder 12, that is at least 5.1 channels, and a digital signal processor (DSP) 14, both of which are located in or otherwise connected to the head unit HU. The head unit HU also includes or is connected to an audio amplifier 16 that drives each of the following eight speaker nodes A-H that are located where shown in FIG. 1 and/or as indicated by their name:
Speaker Node A=Front Left Tweeter/Front Left Door (FL-TW/FL-Door)
Speaker Node B=Front Right Tweeter/Front Right Door (FR-TW/FR-Door)
Speaker Node C=Center (CTR) (typically located in the front of the vehicle)
Speaker Node D=Rear Left Door (RL-Door)
Speaker Node E=Rear Right Door (RR-Door)
Speaker Node F=Left Surround (L-Surr)
Speaker Node G=Right Surround (R-Surr)
Speaker Node H=Subwoofer (Subw) (typically located in the rear of the vehicle)
Each speaker node A-H comprises at least one speaker for output of sound. The head unit HU further includes or is connected to a fader 18 that varies the audio signal power or gain for each of the audio signals output from the amplifier 16 to the various speaker nodes A-H.
A video viewing region VR is defined in the vehicle V and comprises all seating locations except the driver and front-seat passenger. Passengers seated in the video viewing region VR are able to face forward and view the one or more video display monitors M that are active to display video images of movies and the like. A subset D-H of said speaker nodes A-H is located in said video viewing region VR.
More particularly, FIG. 2 shows that the DVD player or other multi-channel audio source 10 outputs its surround sound audio signal to the decoder 12 that derives and outputs the 5.1 channel surround sound audio channel signals from the received surround sound audio signal as follows: (i) Front Left; (ii) Front Right; (iii) Center; (iv) Rear Left; (v) Rear Right; (vi) Subwoofer. These surround sound audio signals are output from the decoder 12 to the DSP 14 which filters, conditions, adjusts, and otherwise derives at least ten surround sound speaker signals that are output to the eight respective speaker nodes A-H through to an amplifier 16 that amplifies each of the 10 surround sound speaker signals according to the setting of the fader 18. It can be seen in FIG. 2 that the head unit HU is configured and programmed such that the DSP 14 maps the surround sound speaker signals to the speaker nodes as follows:
Front LeftSpeaker Node AFront RightSpeaker Node BCenterSpeaker Node CRear LeftSpeaker Node DRear RightSpeaker Node ERear LeftSpeaker Node FRear RightSpeaker Node GSubwooferSpeaker Node H
FIG. 2 also shows three different fader levels as controlled by the fader 18: Fader Center, Fader Rear +x, Fader Rear Max. For the “Fader +x” and “Fader Rear Max” positions, the sound output within the vehicle V is biased toward the video viewing region VR in the rear of the vehicle (Fader Front +x and Fader Front Max are also available but not pertinent to the present discussion). At the “Fader Center” position, the amplifier 16 outputs full or max audio signal power level to all speak nodes A-H as shown. At the “Fader Rear +x” position, the amplifier 16 outputs an attenuated “−x” audio signal power level to the speaker nodes A-C, and outputs the full max audio signal power level to speaker nodes D-H. At the “Fader Rear Max” position, the amplifier 16 outputs the “minus infinity” or “−∞” audio signal power level to speaker nodes A-C (indicating no sound), and outputs the full max audio signal power level to speaker nodes D-H that define the subset of speaker nodes located in the video viewing region VR.
It is apparent in FIG. 2 that the system S is configured and programmed such that changes in the fader state between the “Fader Center” “Fader Rear +x” and “Fader Rear Max” levels changes only the gain in the audio signal power level output to some of the speaker nodes A-H to control the sound volume output from the various speaker nodes A-H, while the mapping of the surround sound speaker signals from the DSP 14 to the speaker nodes A-H is unchanged. As such, when occupants of the vehicle V located in the video viewing region VR are viewing a DVD or other video on the monitor(s) M and the fader 18 is adjusted to “Fader Rear +x” or “Fader Rear Max,” as is often the case when the front-seat passengers cannot see the video display monitor(s) M and do not want to be distracted by the associated sound, the Front Left, Front Right and Center surround sound audio signals output from the DSP 14 and amplifier 16 are reduced or eliminated, which can degrade the surround sound experience for the passengers in the video viewing region VR of the vehicle V that are viewing the video images on the monitor(s).
A drawback of such prior systems is that when the fader is controlled to bias the sound toward the rear of the vehicle for viewing of a DVD or other video including surround sound audio, some of the surround sound audio signals are attenuated or even completely omitted from playback through the vehicle speaker system. Such an approach does not provide a true surround sound audio experience to those vehicle passengers viewing the video.